Carrier aggregation, in which a wireless communications device simultaneously transmits and/or receives radio frequency (RF) signals over multiple RF frequency bands, has become increasingly popular in order to maximize data throughput. Supporting carrier aggregation in a wireless communications device presents several challenges in the design and manufacture of the device. FIG. 1 is a functional schematic of conventional radio frequency (RF) front end circuitry 10 suitable for performing both uplink carrier aggregation in which multiple RF transmit signals in different operating bands are simultaneously transmitted and downlink carrier aggregation in which multiple RF receive signals in different operating bands are simultaneously received. The conventional RF front end circuitry 10 includes primary communications circuitry 12, secondary communications circuitry 14, and control circuitry 16. The primary communications circuitry 12 is coupled to a primary antenna 18. The secondary communications circuitry 14 is coupled to a secondary antenna 20. The primary communications circuitry 12 and the secondary communications circuitry 14 are coupled to one another via a first antenna swapping line 22A and a second antenna swapping line 22B. The control circuitry 16 is coupled to both the primary communications circuitry 12 and the secondary communications circuitry 14.
The primary communications circuitry 12 includes antenna swapping circuitry 24 coupled between the primary antenna 18 and primary front end switching circuitry 26, primary RF filtering circuitry 28 coupled between the primary front end switching circuitry 26 and a number of band switches 30, and a number of primary RF power amplifiers 32 coupled to the band switches 30. The primary front end switching circuitry 26 includes a number of primary front end switching elements SW_PFE configured to selectively couple one or more filtering elements in the primary RF filtering circuitry 28 to the antenna swapping circuitry 24. The primary RF filtering circuitry 28 includes a reconfigurable multiplexer 34A and a heptaplexer 34B. The reconfigurable multiplexer 34A is coupled between a first common node 36 and a first set of input/output nodes 38. The heptaplexer 34B is coupled between a second common node 40 and a second set of input/output nodes 42.
The reconfigurable multiplexer 34A includes a pentaplexer 44A, a receive filter 44B, and a duplexer 44C. The pentaplexer 44A is configured to pass primary RF transmit signals within a first operating band, a second operating band, and a third operating band between a first one of the first set of input/output nodes 38A and the first common node 36 while attenuating other signals in this path, pass primary RF transmit signals within a fourth operating band between a second one of the first set of input/output nodes 38B and the first common node 36 while attenuating other signals in this path, pass primary RF receive signals within the first operating band between the first common node 36 and a third one of the first set of input/output nodes 38C while attenuating other signals in this path, pass primary RF receive signals within the second operating band, the third operating band, and the fourth operating band between the first common node 36 and a fourth one of the first set of input/output nodes 38D while attenuating other signals in this path, and pass primary RF receive signals within a fifth operating band between the first common node 36 and a fifth one of the first set of input/output nodes 38F while attenuating other signals in this path.
The receive filter 44B is configured to pass primary RF receive signals within a sixth operating band between the first common node 36 and a sixth one of the first set of input/output nodes 38F while attenuating other signals in this path.
The duplexer 44C is configured to pass primary RF transmit signals within a seventh operating band between a seventh one of the first set of input/output nodes 38G and the first common node 36 while attenuating other signals in this path and pass primary RF receive signals within the seventh operating band between the first common node 36 and an eighth one of the first set of input/output nodes 38H while attenuating other signals in this path.
The heptaplexer 34B is configured to pass primary RF transmit signals within the second operating band between a first one of the second set of input/output nodes 42A and the second common node 40 while attenuating other signals in this path, pass primary RF transmit signals within an eighth operating band between a second one of the second set of input/output nodes 42B and the second common node 40 while attenuating other signals in this path, pass primary RF transmit signals within a ninth operating band between a third one of the second set of input/output nodes 42C and the second common node 40 while attenuating other signals in this path, pass primary RF receive signals within the eighth operating band between the second common node 40 and a fourth one of the second set of input/output nodes 42D while attenuating other signals in this path, pass primary RF receive signals within the second operating band between the second common node 40 and a fifth one of the second set of input/output nodes 42E while attenuating other signals in this path, pass primary RF receive signals within the ninth operating band between the second common node 40 and a sixth one of the second set of input/output nodes 42F while attenuating other signals in this path, and pass primary RF receive signals within a tenth operating band between the second common node 40 and a seventh one of the second set of input/output nodes 42G while attenuating other signals in this path.
The primary front end switching circuitry 26 may selectively couple the receive filter 44B to the pentaplexer 44A when the conventional RF front end circuitry 10 is receiving in the sixth operating band, connect the duplexer 44C to the pentaplexer 44A when the conventional RF front end circuitry 10 is transmitting and/or receiving in the seventh operating band, or isolate the receive filter 44B and the duplexer 44C from the pentaplexer 44A when the conventional RF front end circuitry 10 is not transmitting or receiving in the sixth operating band or the seventh operating band. Those skilled in the art will appreciate that providing the reconfigurable multiplexer 34A in this manner may allow the primary RF filtering circuitry 28 to support a desired number of operating bands while reducing loading in the RF signal path of the primary communications circuitry 12. The primary front end switching circuitry 26 may connect the antenna swapping circuitry 24 to one of the reconfigurable multiplexer 34A (the configuration of which is set by the primary front end switching circuitry 26 as discussed above) or the heptaplexer 34B, depending on the operating bands in which the conventional RF front end circuitry 10 is transmitting and/or receiving.
The first primary RF power amplifier 32A may be configured to amplify RF transmit signals within the first operating band, the second operating band, and the third operating band. Depending on the operating band or operating bands in which the first primary RF power amplifier 32A is transmitting and the operating band or operating bands in which the conventional RF front end circuitry 10 is receiving, a number of primary band switches SW_PB in a first band switch 30A may couple the first primary RF power amplifier 32A to one of the reconfigurable multiplexer 34A or the heptaplexer 34B.
The second primary RF power amplifier 32B may be configured to amplify RF transmit signals within the fourth operating band and the eighth operating band. Depending on the operating band or operating bands in which the second primary RF power amplifier 32B is transmitting and the operating band or operating bands in which the conventional RF front end circuitry 10 is receiving, a number of primary band switches SW_PB in a second band switch 30B may couple the second primary RF power amplifier 32B to one of the reconfigurable multiplexer 34A or the heptaplexer 34B.
The third primary RF power amplifier 32C may be configured to amplify RF transmit signals within the seventh operating band. Depending on the operating band or operating bands in which the third primary RF power amplifier 32C is transmitting and the operating band or operating bands in which the conventional RF front end circuitry 10 is receiving, a number of primary band switches SW_PB in a third band switch 30C may selectively couple the third primary RF power amplifier 32C to the reconfigurable multiplexer 34A. Since the third primary RF power amplifier 32C does not provide RF transmit signals in an operating band supported by the heptaplexer 34B, the third band switch 30C does not connect thereto. While not shown, additional switches in the first band switch 30A, the second band switch 30B, and the third band switch 30C may couple the respective primary RF power amplifiers 32 to additional filters in the primary RF filtering circuitry 28.
While not shown, a number of low-noise amplifiers (LNAs) may connect to the remaining input/output nodes in the first set of input/output nodes 38 and the second set of input/output nodes 44 in order to amplify receive signals therefrom for further processing.
The secondary communications circuitry 14 includes antenna swapping circuitry 46 coupled between the secondary antenna 20 and secondary front end switching circuitry 48 and secondary RF filtering circuitry 50 coupled to the secondary front end switching circuitry 48. The secondary front end switching circuitry 48 includes a number of secondary front end switching elements SW_SFE configured to selectively couple one or more filters in the secondary RF filtering circuitry 50 to the antenna swapping circuitry 46. The secondary RF filtering circuitry 50 includes a first triplexer 52A and a second triplexer 52B. The first triplexer 52A is coupled between a first common node 54 and a first set of input/output nodes 56. The second triplexer 52B is coupled between a second common node 58 and a second set of input/output nodes 60.
The first triplexer 52A is configured to pass secondary RF receive signals within the second operating band, the third operating band, and the fourth operating band between the first common node 54 and a first one of the first set of input/output nodes 56A while attenuating other signals in this path, pass secondary RF receive signals within the eighth operating band between the first common node 54 and a second one of the first set of input/output nodes 56B while attenuating other signals in this path, and pass secondary RF receive signals within the ninth operating band between the first common node 54 and a third one of the first set of input/output nodes 56C while attenuating other signals in this path.
The second triplexer 52B is configured to pass secondary RF receive signals within the first operating band between the second common node 58 and a first one of the second set of input/output nodes 60A while attenuating other signals in this path, pass secondary RF receive signals within the second operating band and the fourth operating band between the second common node 58 and a second one of the second set of input/output nodes 60B while attenuating other signals in this path, and pass secondary RF receive signals within the seventh operating band between the second common node 58 and a third one of the second set of input/output nodes 60C while attenuating other signals in this path.
While not shown, a number of LNAs may connect to the first set of input/output nodes 56 and the second set of input/output nodes 60 in order to amplify receive signals therefrom for further processing.
The antenna swapping circuitry 24 in the primary communications circuitry 12 and the antenna swapping circuitry 46 in the secondary communications circuitry 14 are coupled via the first antenna swapping line 22A and the second antenna swapping line 22B. The antenna swapping circuitry 24 in the primary communications circuitry 12 may cooperate with the antenna swapping circuitry 46 in the secondary communications circuitry 14 to selectively couple one of the primary antenna 18 and the secondary antenna 20 to the primary front end switching circuitry 26 and couple the antenna not coupled to the primary front end switching circuitry 26 to the secondary front end switching circuitry 48.
Those skilled in the art will appreciate that the primary communications circuitry 12 is responsible for transmitting and receiving primary RF transmit signals and primary RF receive signals within one or more operating bands, while the secondary communications circuitry 14 is configured to receive secondary RF receive signals within the one or more operating bands. As discussed herein, primary RF transmit signals and primary RF receive signals are the main transmit and receive signals used for communication, while the secondary RF receive signals are additional signals used to improve reception quality or data throughput. For example, the secondary RF receive signals may be diversity receive signals or multiple-input-multiple-output (MIMO) receive signals.
The first operating band may be Long Term Evolution (LTE) operating band 3 with a transmit frequency of 1710-1785 MHz and a receive frequency of 1805-1880 MHz, the second operating band may be LTE operating band 4 with a transmit frequency of 1710-1755 MHz and a receive frequency of 2110-2155 MHz, the third operating band may be LTE operating band 66 with a transmit frequency of 1710-1780 MHz and a receive frequency of 2110-2200 MHz, the fourth operating band may be LTE operating band 1 with a transmit frequency of 1920-1980 MHz and a receive frequency of 2110-2170 MHz, the fifth operating band may be LTE operating band 40 (TDD) with a receive frequency of 2300-2400 MHz, the sixth operating band may be LTE operating band 41 (TDD) with a receive frequency of 2496-2690 MHz, the seventh operating band may be LTE operating band 7 with a transmit frequency of 2500-2570 MHz and a receive frequency of 2620-2690 MHz, the eighth operating band may be LTE band 25 (which may include LTE band 2) with a transmit frequency of 1850-1915 MHz and a receive frequency of 1930-1995 MHz, the ninth operating band may be LTE operating band 30 with a transmit frequency of 2305-2315 MHz and a receive frequency of 2350-2360 MHz, and the tenth operating band may be LTE operating band 38 (TDD) with a receive frequency of 2570-2620 MHz.
While the conventional RF front end circuitry 10 is capable of both uplink and downlink carrier aggregation, the circuitry may suffer from signal degradation due to intermodulation distortion in certain carrier aggregation configurations. For example, when primary RF transmit signals in the first operating band and the fourth operating band are simultaneously provided from the first primary RF power amplifier 32A and the second primary RF power amplifier 32B, respectively, these signals may intermodulate with one another to produce troublesome intermodulation distortion. As discussed above, the first operating band may be LTE operating band 3, and the fourth operating band may be LTE operating band 1. This combination of LTE operating band 3 and LTE operating band 1 may be problematic, as intermodulation distortion products from the transmit signals of these bands may fall directly into the receive frequency of LTE operating band 1. To avoid desensitization of receiver circuitry configured to process primary RF receive signals in the fourth operating band, the selectivity of the filters in the pentaplexer 44A must be very high, often at levels that are unachievable within common design constraints such as cost and size.
The intermodulation products from simultaneously providing primary RF transmit signals in the first operating band and the fourth operating band may come from a variety of sources. First, the pentaplexer 44A may leak a small amount of the primary RF transmit signals in the fourth operating band backwards from the output of the second primary RF power amplifier 32B to the output of the first primary RF power amplifier 32A. These leakage signals will intermodulate with the primary RF transmit signals in the first operating band in the first band switch 30A. The same process will also occur from the first primary RF power amplifier 32A to the second primary RF power amplifier 32B in the second band switch 30B. Additionally, signals from the first primary power amplifier 32A will also leak to the second primary power amplifier 32B, where they may be amplified by the second primary power amplifier 32B to produce significant intermodulation distortion products. Second, the combination of the primary RF transmit signals within the first operating band and the fourth operating band will intermodulate in the primary front end switching circuitry 26 and the antenna swapping circuitry 24. The intermodulation distortion produced therefrom will flow back through the pentaplexer and to receive circuitry attached thereto absent a very high selectivity filter. As discussed above, such a filter may not be achievable within common design constraints, and thus the intermodulation will cause desensitization of downstream receive circuitry.
For the reasons described above, there is a need for improved RF front end circuitry capable of operating in carrier aggregation modes without excessive intermodulation.